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October 2014

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From:
Frank Levine <[log in to unmask]>
Reply To:
Frank Levine <[log in to unmask]>
Date:
Tue, 28 Oct 2014 14:11:03 -0400
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If you're using the Gyro, you'll want to make sure you're resetting it
properly.  The best gyro reset code that we have found comes from the Hoosier
Girlz <http://www.fllhoosiergirlz.com/> via Droid Robotics
<http://www.ev3lessons.com/advanced.html> advanced lesson #5.  If your Gyro
occasionally starts to drift, this is for you...

While gyro is calibrating, it returns 'NaN' which stands for "Not a
Number".  NaN's are a serious pain and cause all sorts of problems in real
world code.  Taking the square root of -1 is one way to geneate a NaN in
'real' programming languages.  Anyways, NaN's have the interesting property
that they return false when compared to other numbers.  This allows the
clever EV3 programmer (ie, the Hoosier Girlz) to detect them and wait for
the Gyro to reset.
Step 1: Read both the Angle and Rate at the same time
Step 2: Start a loop
Step 3: Read the angle
Step 4: Check to see if the Angle is >= 0
Step 5: Check to see if the angle is < 0
Step 6: "or" the results of steps 4,5 together
If the result of step 6 is true, then the number is >=0 or <0 so you're
good to go
If the result of step 6 is false, then the number must be NaN (it's not >=0
or <0) so repeat the loop.

This solved all of our Gyro drift problems and I think it is something that
all teams should know and understand.  Honestly, the 'reset' block should
have come standard with the EV3 environment.  It's hard enough to use the
Gyro when it's calibrated correctly.  When it's not it can waste valuable
team time.

In response to Droid Robotic's efforts, our team shared their Proportional
Control turn code (which is made even better with a calibrated gyro!).  If
your teams have any basic building blocks that they want to share, the guys
at Droid Robotics appear to be compiling a very nice set of building blocks
that are easy to understand and explain to FLL kids.  What I like about
them is that they don't just re-post solutions, they take the time to
understand what's going on and explain it in a way that kids their age will
understand.  I think it's a great project and I fully support what they're
doing.

Thanks,
Frank Levine
Coach "The Construction Mavericks"







On Tue, Oct 28, 2014 at 1:49 PM, Nancy Nguyen <[log in to unmask]> wrote:

> Just goes to show you that every team is different and has different
> experiences. My team has had great success with the gyro sensor. Does not
> affect the speed of our robot and makes nice precise turns in tight spaces.
> The kids have not been very successful with the color sensor. They feel it
> is more trouble than it's worth. Like I said, different experiences for
> different teams.
>
> Sent from my iPhone
> -Nancy Nguyen
>
> On Oct 28, 2014, at 1:03 PM, MARVIN HOM <[log in to unmask]> wrote:
>
> Try scrimmaging against a team that uses sensors. The improvement with
> sensors vs no sensors will be obvious.
>
> ..but don't use the gyro. It can be made to work reliably but it's
> performance will be agonizingly slow.
>
> -Regards,
> Marvin Hom
> Coach
> Falls Church, VA
>
> On Oct 28, 2014, at 12:51 PM, Betsy T. Wilco <[log in to unmask]> wrote:
>
> Honestly, I want my kids to learn to use sensors, but before tournament I
> am very "hands-off" with any building or programming. I ask them questions,
> I cheer them on, but all decisions are made by the kids. So my opinion is
> that if they don't want to use sensors, they should be alloewed to make
> that decision.  Possibly they just aren't ready. But in any case, they will
> learn a ton from participating at all. They will see other teams using
> different methods at tournament and want to try some of them when they come
> back. And, next year the experienced kids may encourage the newbies to new
> heights. Or not. But it is their work, their bot, their strategy that
> counts. Just one opinion!
>
> *Betsy T Wilco*
> *Gifted Resource Teacher*
> *Prince William County Schools*
> *703.754.9061 <703.754.9061>*
> ------------------------------
> *From:* First Lego League in Virginia and DC <[log in to unmask]>
> on behalf of VA-DC Referee Advisor <[log in to unmask]>
> *Sent:* Tuesday, October 28, 2014 12:47 PM
> *To:* [log in to unmask]
> *Subject:* Re: [VADCFLL-L] Between runs
>
> I haven't been an FLL coach, but you might try the blindfolded
> instructions approach:
>
> Go forward 4 steps.  Turn right.  Move forward until you hit the wall.
> Turn left.  Go three steps.  Line yourself up with the table.  etc...
>
> It's fun for team building, too!
>
> Steve
>
> On Tue, Oct 28, 2014 at 12:33 PM, Fredrik Nyman <[log in to unmask]>
> wrote:
>
>> Somewhat off-topic, but:
>>
>> I'm having a hard time getting my kids to use sensors.  Since the sensors
>> (color and gyro in particular) are pretty finicky, the kids think that
>> there isn't much of an advantage of using them compared to doing navigation
>> in terms of motor rotations.
>>
>> How is everyone else doing?  Have you found a way to convince the kids
>> that the sensors are worthwhile?
>>
>>
>>
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